JPS6221728Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to an air-fuel ratio control device for an internal combustion engine.

Conventionally, in order to purify the exhaust gas from the internal combustion engine, air-fuel ratio control for an internal combustion engine detects the oxygen concentration in the exhaust gas of the internal combustion engine and controls the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine according to the detection result. A device has been proposed, and if this control is performed over the entire operating state of the internal combustion engine, the required output cannot be obtained during acceleration, etc. when high output is required from the internal combustion engine, and if fuel is cut during deceleration, the fuel cut ends. Sometimes the air-fuel mixture becomes too rich, causing problems with exhaust gas purification.
Transient operation of an internal combustion engine in which integral processing is performed according to the detected value from the air-fuel ratio detector, the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine is corrected according to this integral processed value, and the throttle valve is fully opened or fully closed. In some cases, a device has been proposed that continues the integral processing value obtained immediately before the throttle valve is fully opened or fully closed. The air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine is controlled, for example, by a carburetor installed in the intake circuit of the internal combustion engine and an actuator attached to the carburetor to increase or decrease the amount of bleed air in the carburetor. When transitioning from a deceleration state to an idle state, if the idle air-fuel ratio control is continued at the same level as the control bleed air amount before deceleration, the air-fuel ratio will become over lean and cause an engine stall problem.
To improve this, the air-fuel ratio is controlled for a certain period of time after the vehicle enters a deceleration state, and then the level of the bleed air volume is temporarily lowered to control the bleed air volume to the optimal air volume for the idle state. This has traditionally been done. However, with this method, if the internal combustion engine shifts to an idle state while the air-fuel ratio is being controlled within a predetermined period of time (the above-mentioned fixed time) after shifting to a deceleration state, the amount of bleed air is still at a high level. On the other hand, shortening the time for air-fuel ratio control after transitioning to a deceleration state would lead to an increase in HC and CO during deceleration, which would worsen emissions.

The present invention is intended to solve the above-mentioned problems in the prior art.If the internal combustion engine shifts to an idle state while the air-fuel ratio is being controlled within a predetermined period of time after the vehicle is decelerated, the air-fuel ratio is immediately adjusted. An object of the present invention is to provide an air-fuel ratio control device that can enrich the air-fuel ratio of an air-fuel mixture and prevent engine stall.

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration in which an air-fuel ratio control device according to the present invention is combined with an internal combustion engine. In the overall configuration shown in FIG. It is a vaporizer equipped with
An actuator 3 that adjusts the air-fuel ratio separately from the throttle valve is attached to the carburetor 2, and the carburetor 2 and actuator 3 control the air-fuel ratio of the air-fuel mixture supplied to the engine 1 via the intake passage. A fuel metering device 4 is configured. The actuator 3 is a carburetor 2 that supplies the intake passage.
The actuator 3 is composed of a linear solenoid valve that increases or decreases the amount of bleed air.
The opening/closing operation of the valve is controlled by the applied current, and the air-fuel ratio is made lean when the valve is opened.
Note that, as shown by the chain line, the actuator 3' may not be attached to the carburetor 2 but may be attached to the intake manifold section to form a secondary air supply device. Further, reference numeral 5 denotes an oxygen concentration detector which is provided at the exhaust pipe gathering part and detects the oxygen concentration in the exhaust gas;
7 is a comparison circuit that outputs a deviation signal between the output of the oxygen concentration detector 5 and a set value corresponding to the stoichiometric air-fuel ratio; 7 is an integration circuit that outputs an integral signal of the deviation signal of the comparison circuit 6; 8 is an integral voltage; This is an actuator drive circuit that controls the current applied to the actuator 3 accordingly. Reference numeral 9 denotes an engine rotation sensor, which inputs the primary waveform of the ignition coil in the present invention, but it may also input the pick-up waveform of the igniter. Reference numeral 10 denotes the engine rotation speed detection circuit, which compares the engine rotation speed with a preset rotation speed and outputs a deviation signal. Reference numeral 11 denotes a vacuum sensor, which detects negative pressure in the intake system and determines the engine condition, and is usually provided at the bottom of the throttle positioner (TP port). 12
is a buffer circuit for the vacuum switch signal, and the output signal and the engine rotation speed detection circuit 1 are
A deviation output of 0 is input to the deceleration detection circuit 13, it is determined whether or not the engine is in a deceleration state, and if the engine is in a deceleration state, a deceleration signal is input to the timer circuit 14, the air-fuel ratio control is continued for a predetermined time, and the deceleration signal is input to the timer circuit 14. If the deceleration state continues even after that, the feedback stop circuit 15 is configured to stop the air-fuel ratio control. 16 is a timing circuit, which is connected to the engine rotation speed detection circuit 10.
Input the output of and the signal of the vacuum sensor 11,
If the engine speed decreases within the predetermined period of time in the deceleration state and shifts to the idle state, a feedback stop signal is immediately output to the feedback stop circuit 15.

FIG. 2 is an electrical circuit diagram of the embodiment of the present invention shown in FIG. 1, and FIG. 3 is a time chart thereof. In the comparator circuit 6, a set value corresponding to the stoichiometric air-fuel ratio is connected to the non-inverting input terminal of the comparator 61 via a resistor 6.
2 and 63, and the output signal of the oxygen concentration detector 5 is input to the inverting input terminal, and these are compared using the divided voltages to obtain a deviation output. When the exhaust gas air-fuel ratio is rich (hereinafter referred to as "rich"), the output of the comparison circuit 6 becomes "L" level because the output of the oxygen concentration detector 5 is "H" level, and when the exhaust gas air-fuel ratio is lean (hereinafter referred to as "lean"), the output of the comparison circuit 6 becomes "L" level. In this case, since the output of the oxygen concentration detector 5 is at the "L" level, the output of the comparison circuit 6 is at the "H" level. Integral circuit 7
receives the output of the comparator circuit 6, and when the exhaust gas air-fuel ratio is rich, the output of the comparator 61 becomes "L" level, so the capacitor 72 is charged through the resistor 71, the output of the integrating circuit 7 rises, and the actuator The drive circuit 8 supplies a current corresponding to the integral voltage to the actuator 3, and the actuator 3 operates in the valve opening direction to increase the amount of bleed air and lean the control air-fuel ratio.

When the exhaust gas air-fuel ratio is lean, the comparison circuit 61
Since the output becomes "H" level, the capacitor 72 is reversely charged through the resistor 71, the output of the integrating circuit 7 decreases, and the actuator 3 operates in the valve closing direction to enrich the air-fuel ratio.

In the engine rotation speed detection circuit 10, 101
is an F/V converter that generates a voltage corresponding to the engine speed, and this voltage is compared by a comparator 102 with the voltage set by resistors 103 and 104, and outputs a deviation signal. Therefore, if the engine speed is below the set value, an output signal of "H" level is generated, and if it is above the set value, an output signal of "L" level is generated.

When the engine is running steadily and the throttle valve is open, the negative pressure below the throttle valve is close to atmospheric pressure, and the vacuum sensor 11 is closed. Thereafter, when the deceleration state is entered, the throttle valve is closed and negative pressure is generated, the vacuum sensor 11 is opened, the transistor 121 of the buffer circuit 12 is turned on, and the collector voltage of the transistor 121 is
It becomes 0V. Further, in the deceleration state, the engine speed naturally increases, and the output of the engine speed detection circuit 10 goes to "L" level, and both inputs of the deceleration detection circuit 13 go to "L" level, so the transistor 131 becomes non-conductive. The collector voltage becomes "H" level, the capacitor 141 of the timer circuit 14 is charged through the resistors 132 and 142, and the capacitor voltage rises with a time constant of RC. 143 is a comparator, and when the charging voltage of the capacitor 141 rises above the voltage set by the resistors 144 and 145 after a preset time has elapsed, the output of the comparator 143 becomes "L" level, and the feedback stop circuit is activated. 15 transistors 151
The base of is biased through resistors 152 and 153, transistor 151 becomes conductive, capacitor 72 is rapidly charged through resistor 154 having a small resistance value, and the integral output rapidly decreases to stop air-fuel ratio control. That is, when the time set by the timer circuit 14 has elapsed, the integral value is reset and the air-fuel ratio control is stopped.

In the case where the timing circuit 16 is not provided when the engine speed falls below the set speed during the set time set by the timer circuit 14, the output of the engine speed detection circuit 10 becomes "H". level, and the transistor 131 of the idle detection circuit 13 is biased through the resistor 132 and conducts. The capacitor 141 of the timer circuit 14 is rapidly discharged through the resistor 142 with a small resistance value, and as a result, the output of the comparator 143 becomes "H" level. , the transistor 151 of the feedback stop circuit 15 becomes non-conductive, the integration circuit 7 performs integration in accordance with the output of the comparison circuit 6, and the air-fuel ratio control is restarted. However, in the present invention, when the vacuum sensor 11 is in the open state, the cathode of the diode 161 becomes "H" level, and when the output at engine speed 10 switches from "L" level to "H" level, by the timing circuit 16, The capacitor 162 and the resistor 16 are connected to each other at the timing when the engine speed changes from high to low (point a in Fig. 3).
A pulse waveform as shown in FIG. 3 is generated with a time constant of 3,164,165, and the transistor 166 is turned on for a certain period of time in a pulsed manner as shown in FIG. 155 for a certain period of time.
Therefore, the integral output of the integrating circuit 7 rapidly decreases, the air-fuel ratio control is stopped, and the air-fuel ratio control is restarted from a low air-fuel ratio correction amount corresponding to the idle air-fuel ratio after deceleration, thereby improving emissions.

FIG. 4 is a block diagram of an embodiment in which a microcomputer is used in the present invention. Components in FIG. 4 that are the same as those shown in FIGS. 1 and 2 are given the same reference numerals. 17 is a one-chip microcomputer, 18 is an A/
It is a D (analog/digital) converter. 19
is a control signal line of the A/D converter 18, 20 is an A/D conversion end signal, and 21 is a data signal line after A/D conversion. The signal output from the one-chip microcomputer 17 to the actuator drive circuit 8 is a duty signal, and the actuator drive circuit 8 supplies a current corresponding to this duty signal to the actuator 3.
This is a circuit configuration that supplies electricity to the 22 is a waveform shaping circuit for the engine speed sensor 9, and its output is input to an external interrupt terminal of the one-chip microcomputer 17.

The flowchart shown in FIG. 5 is the main program of the embodiment of the present invention shown in FIG. 4, and FIG. 6 is the program when an interrupt occurs in the engine rotation sensor. Note that FIG. 7 shows the data area of the RAM area. In FIG. 5, the initial setting of the one-chip microcomputer 17 is performed,
The output of the oxygen concentration detector 5 is A/D converted by an A/D converter 18, and the data signal after A/D conversion is input to a one-chip microcomputer 17. Next, the signal from the vacuum switch 11, which determines the throttle position of the vehicle, is transferred to the buffer circuit 12.
Through one chip microcomputer 17
Enter the same in .

Thereafter, the one-chip microcomputer 17 determines whether or not the vehicle is in a deceleration state, and after shifting to the deceleration state, the delayed air-fuel ratio feedback by the delay timer 1 is stopped. Additionally, if the vacuum switch is open and the engine speed changes from higher to lower than the predetermined rotation speed, one-shot timer 2 will stop the air-fuel ratio feedback for a predetermined period of time, and then restart the air-fuel ratio feedback. do.

As described above, according to the present invention, when the internal combustion engine rotation speed falls below the set rotation speed while the air-fuel ratio is being controlled for a predetermined period when the vehicle shifts to a deceleration state and the vehicle shifts to an idle state, Immediately, the air-fuel ratio control based on the air-fuel ratio deviation integral value is stopped and the air-fuel ratio control is performed from the state where the integral value is reset, so that the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine when the state shifts to the above-mentioned idle state is It is possible to obtain the excellent effect of preventing engine stall by making the engine richer. According to the present invention, it is not necessary to shorten the predetermined time for performing air-fuel ratio control when the vehicle shifts to a deceleration state, and deterioration of emissions can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the air-fuel ratio control device according to the present invention combined with an internal combustion engine, Fig. 2 is an electric circuit diagram of the embodiment shown in Fig. 1, and Fig. 3 is an electric circuit diagram of the embodiment shown in Fig. 2. Fig. 4 is a block diagram of another embodiment of the air-fuel ratio control device according to the present invention using a microcomputer, and Fig. 5 is a main program of the embodiment shown in Fig. 4. FIG. 6 is a flowchart showing a program when an interrupt occurs in the engine rotation sensor in the embodiment of FIG. 4, and FIG. 7 is a diagram showing the data area of the RAM area in the embodiment of FIG. 4. It is. DESCRIPTION OF SYMBOLS 1... Engine, 2... Carburizer, 3... Actuator, 4... Fuel metering device, 5... Oxygen concentration detector, 6... Comparison circuit, 7... Integrating circuit, 8...
... Actuator drive circuit, 9 ... Engine rotation speed sensor, 10 ... Engine rotation detection circuit, 11
... Vacuum switch, 12 ... Buffer circuit, 13 ... Deceleration detection circuit, 14 ... Timer circuit, 15 ... Feedback stop circuit, 16 ...
Timing circuit, 17...Microcomputer, 18...A/D converter, 22...Waveform shaping circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) An air-fuel ratio control device that detects the air-fuel ratio of exhaust gas of an internal combustion engine and controls the air-fuel ratio of a mixture supplied to the internal combustion engine according to the detected value, a detector that detects an air-fuel ratio of exhaust gas from an internal combustion engine;
an internal combustion engine rotation speed sensor, an engine load state detection means, and an air-fuel ratio of exhaust gas outputted from the detector to a predetermined air-fuel ratio determined in advance to obtain a deviation value and integrate the deviation value. A control device that generates an air-fuel ratio control signal with a value corresponding to a value, and receives the output of an internal combustion engine rotation speed sensor and an engine load state detection means, and when a vehicle equipped with an internal combustion engine shifts to a deceleration state. After the air-fuel ratio control continues for a predetermined period of time, the air-fuel ratio control is stopped, and if the rotational speed of the internal combustion engine falls below a predetermined set value during the period and the internal combustion engine shifts to an idle state, the control is immediately performed. An air-fuel ratio control device comprising: a control device that stops air-fuel ratio control; and a device that adjusts an air-fuel ratio of an air-fuel mixture supplied to an internal combustion engine in accordance with the air-fuel ratio control signal. (2) Utility model registration The air-fuel ratio control device according to claim 1, wherein the control device is a device that generates a deviation value signal representing a difference between the output of the detector and a predetermined air-fuel ratio. , an integrating means that integrates the deviation value signal to generate an air-fuel ratio control signal, and a timer means that detects that the vehicle has shifted to a deceleration state and generates a timer signal after the predetermined time elapses; a timing means for detecting that the rotational speed of the internal combustion engine has fallen below the set value and that the internal combustion engine has entered an idle state, and generating a pulse signal synchronized with the decrease in the rotational speed of the internal combustion engine from the set value; and the timer signal. and a device for resetting the integral value of the integrating means in response to a pulse signal and stopping air-fuel ratio control. (3) Utility Model Registration The air-fuel ratio control device according to claim 1, wherein the control device is constituted by a microcomputer.